Answer
31,200,000
Explanation
Firstly, calculate the constant of proportionality.
Al â N
Al = kN Â Â Where Al = number of aluminium cans, k = constant and N = number of people using the can.
Al = kN
k = Al/N
 = 120000/500
 = 240
Equation becomes;
Al = 240N
For 130000 cans;
Al = 240 Ă 130000
  = 31,200,000